Trunnion bearing



L A N E S R A L R H TRUNNION BEARING 2 S-Sk-EET l.

Filed April 2, 1947 Brmentor Harold RLa'rsen and Daniel, Gurney ttomegs Patented July 8, 1952 acoazzo s rfrmmiuou BEARING HaroldR. Larsen, Troy, and Daniel* Gurney,

Jamestown, N. Y., assignors'toW. & VL.1E."(rur j ley, Troy, N. Y., a corporationv otNew York Application Apr-i12, 1947, Serial No. 739,034

- ThisV invention relates togeometricalinstruments of the light-ray type and particularly to transits and theodolites. f -1 v A 'l The patent to 'Larsen and-Sonderman #2,363,- 877, issued November- 28, 1944, f describes an optical micrometer which will measure-angles without interpolation lto '-o'nefsecond of fare. As a 'consequence of this high precisio'nof measurement there is now need for'g'reater accuracyof thebearings` on which the movableelements 'of the surveying instrument 'are mounted. rTheA invention provides an instrument having freeturnlng bearings of great accuracy.

As a basisfory disclosure and discussiomthe lin-v vention will be described as applied to thetrunnion bearings which support the telescope of a theodolite. In the'past it vhasbeen customaryto use plain bearings ofthe precision type tofsupportthe trunnions on the standards. No matter howprecise such a'bearing may be, some *clearance *betweenv the journal andA the bearing isan Vabsolute necessity. Thus, when-the telescope is swung on its trunnions there is a minutetendency for the journals to climb in the bearings. vIf a tangent screw and clamp are used they must be vlocated'nearer one than vthe other of the two trunnion bearings. Since the tangent screw does not I develop a balanced torque, the effect'is to cause 15 Claims. (Cl. 33 46) one 'trunnion journal to climb more than :the

other. vThe eiect is to produce a lateral deflecvery objectionable. y Y In rst order survey Work.it is common prac- :tice to avoiduse of the tangent screw and toposi- Ation the telescope by tapping it with the finger. .The bearing problem is'furtherLcomplicated by the fact that onefof the trunnion bearings-must be adjustable vertically through a very limited range. This fact imposes .a definite limit on the closeness of ftV of both trunnion journals in their bearings.

The present invention is based on the concept that precision requires the elimination of all bearing clearance. To attain: this result, recoursehas been had toa pre-loaded ball bearing, which is specially designed topermit therequired adjustmentl of one of thebearings. The principal novel feature is that the ball races onv..the trunnions are cylindrical surfaces andv theopposed .race surfaces carried by the standards arealsocylindrical.

Theballs are spaced, and held infcircular: series by .retainers which..engage only. the balls,vv and which? are so dimensionedthat the retainers'and the4 ballsmay move within a 'moderatearange in the direction of; the I'common axis-of -thextrunf- .3o tion of the telescope measurable in amount; and

and'has an eye-piece Il.

nions".v It can be demonstrated that the Hinge-of vertical adjustment vof Vthe adjustable Abearing'fis so slight thatthe preloading of theba'llsfis.r not afectedin Vany. material degree by this adjustment.

Bearings ofthe type just described do notretain the trunnions against axial motionfs the second feature of the inventionis the provision of compatible means which are effective tor prevent axialf motion of` the trunnions 'in allad- .justed lpositions vof the adjustable l bearing.

Theinvention `will now be described as l embodied in the. bearings [for the horizontal 'axis'.o'f a theodlite. l i

.Fig,1 is a viewpartly .in elevation and partly in section,vshowing h ow the telescopeis mounted on trunnion bearings r,in the side-standards of a Fig.i2 is-a section on 'the-lineZ-Z of lig.v 1;,V Fig. 3.is:asection on .the line 3. -3 of Fig. v1; l

Fig. :4 .a `face. viewA of .the bear-ing race ofthe non-adjustabletrunnion bearing; and

.Fig. 5 zisza-sectionon the line 5-5.offFig. 51.

Inthedrawing, the base or alidadezof :theinstrumentislindicated atf6,.and carries-two standards 1 fand-8. These standards are shown. as tof a hollow v `configuration usedto house the optical micrometermechanism disclosed `in the Larsen and Sondermanpatent, above mentioned'but not illustrated; in the drawing of the present-application. The standard -1- carries the Viixed or {nonadjustable bearing. The standard 8 carriesth'e `Yadjustable bearing, and it may be mentioned at jthis point thatthe adjustmentismade in avertical direction.

The telescope of .the vtheodolite `is shown at 9. The Ysmall "telescope indicatedat' I2 4the reading telescope forthe optical micrometer and requires no further'discussion. .The vtwo end portions of the main 'telescope v`tube are threaded intov an axis'bar, f3, which commonly wouldbe formed vof aluminum alloy. Fixed to the ends ofthe axis bar lf3 are thefmembers Ill .and I5, on` which the journal races are formed. The parts l'4 and I5 are ofa special. ball bearing steel which is hardenable and .capable of taking a'high iinish. .Atterthe parts I`4.and-l 5 are assembledwith the-axis bar vhigh nish. In-.the example illustrated, the diameterfofthe races -is one inch plus orminus 0.000025. At the same time the. Iconclzventricj zsur.-

VThe. louter bearing faces I8 and I9 are ground in order to provide bearing surfaces for a striding level.

Encircling the races I6 and I'I are the outer bearing race members 22 and 23 which are formed of a similar hardened steel. The inside diameter of the cylindrical races is ground to 1.3123 inches plus or minus 0.000025. Between the inner and outer races are mounted a series of-.balls 2l which in theexample illustrated are of very special quality. Their diameter is .15625 inches, plus or minus 0.000011. stated, it is apparent that the interval between the inner and outer race of each bearing VisVlessy From the dimensions above 'than the diameter of the ballby- .0001 inch.v It

follows that each ball is pre-.loaded van'd subject are intended to be merely illustrative."

The signicant thing is that the inner. raceior;

erage out with the result that the bearing moves for all practicalV purposes as precisely as the groundsurfaces of the inner and, outer races permit. v .l

member 22 'i's'the fixed or non-adjustable member.- Itis held in place by fourcounterbored screws 24. Onits opposite faces it hasut'wo diametrically arranged ribs 25 and .26... These ribs extend horizontally. They engageplane surfaces which turn fwith'the axis bar I3 and are strictly normal tothe axis .of rotation of the axis bar. One of these surfaces is ticity of the dust guard is more than sucient to maintain seals in all adjusted positions of bearing 23.

It should be observed that the retainer rings 35 are not closely confined so that they permit the row of balls to move in the direction of the axis of the trunnion at least through a limited ranger It will also be observed that if ythe geo- Vmetrical axis of the race-member .23 is so adjusted that it does not precisely align with the axis of the race member 22, the journal races Iand I1 will be slightly cocked so that the balls will roll in a slightly elliptical path rather than a truly circular path.

ll5. to actual distortion Within thevelastic'-, range lof l the ball. The diameters given are typical and.v e1-1.01.'

This',v in '.theory, is mechanically faulty, but notvwhen one has a quantitive idea of the actual A section through journal race I6, normal to its axis, would be a true circle one inch in the surface 21 formed on the member I4 at the' inner end of journal I6. The other is the inner plane Surface 28 ofv adisk 29 Xedto-the end-v of lthe member I4. Here, itmay bev stated that the disk '29 is the support which carries the graduatedA limb of the theodolite. -Theiinterval meas- The adjustable-bearing 23 is held in place three counterboredscrews, one of which appears at 3|V on Fig. 1. VThere is. suicient clearance around the screws to permit the bearing 2.3".to be shifted vertically and this vertical adjustment is made byk meansl of three radial'screvvs 32, one of which is visible'in Fig. 1, and all threeof which are visible in Fig. 3'.r The screw clamp 33 may be setup tolock the arm 34.tothe member I5.V A tangent'screw,'not visible in the'drawing, lcoacts with the lower. end of the arm 34 to turn the axis bar onthe horizontal axis. The construction'is 'conventional s'o far-as the clamp and tangent screw are concerned.

The balls 2I in each bearing are held in aligni'nient by annularl retainers '35.' These are drilled radially to receive-the balls 2l` ofy each series and the retainers arepositioned by'and floatv on the teiial,` U-shaped lin cross-section, as clearly shown in Fig. 1. The baseof the U'isfcemented-inthe groove in which it is mounted and the twoarms of the U seal-in the opposite groove. The lasdiameter.

A section through bearing race 22 would be a true circle 1.323 inches in diameter.

`If we now assume that the axis bar is tilted from ever is that theballs would choose a path on the journal andin the bearing which would divide the error between thertwo softhat the error above computed, small as it is,v is probably twice what actually occurs. -V .4; f Y. L f

,Since-theuballsl are under a pre-load of .0001 the error dueto angular displacementwould not materially,effecttheprefload or. the 'ability of the-axisgto rotate 'freely and truly. Somewhat .similalgeometrical considerationsapply to the ribs which prevent end play of theaxisbar.

. It,A follows that the-usefof pre-loaded balls between...Cylindrical races gives free action and permits limitedrangular ladjustment ofthe axis. Used with -means4 to prevent axial `displacement `of thev axis-banafbearing of the type described very satisfactorily-'meets the requirements of the service.' It-'is truegof course, thatjeach ball has only-slightly moredthfan a point `contact. jHoW- implied." -Modifications Within the scopeof the claims are possible and contemplated. I '.What is claimed is:v f f.

1. Irna geometrical instrument, the combination ofa. support including va pair of spaced standards; an -angularly adjustable member having bearing-supportingv trunnions provided -with lrespective axially alined cylindrical ball Ybearing racesfabout the alined axes of which said member is angularlyadjustable; respective 'bearing mem- .bersi carried by :said standards, each' having a cylindrical'fball race `opposed to a corresponding trunnion ballirace, onev of said .bearingY members Ib'eing. vadjustable on .its standard by right-line .translatorymotionfin a direction transverse to -75 theaxisfof .'theitrunnion; two annular series of land normal to the axis thereof, and stop means fixed relatively to the standards and shaped to enter into substantially diametric line contacts with both said surfaces, said linecontacts approximating coincidence with the axis of tilt of the trunnion axis during adjustment of the; adjustable bearing member.

2. The combination with the vdevice defined in claim 1, of ball retainers Which engage only the balls of a bearing to space andaline the same, said retainers and the balls having a limited freedom of motion in the direction of the axis of the trunnions.

3. The combination defined in claim 1 in which said stop meansxed relatively to the standards comprise diametric ribs lying in a common plane and projecting from the opposite end faces of the standard-carried bearing member.

4. The combination defined in claim 1 in which each standard-carried bearing member is annularly grooved, and the trunnions are provided with opposed faces which have registering annular grooves and universely flexible annular sealsj are provided and extend into opposed grooves, the flexibility of the annular seals being sufcient to accommodate the maximum adjustment.

5. In a geometrical instrument, the combination of a support including a pair of spaced standards; an angularly adjustable member having oppositely projecting supporting trunnions provided with respective axially alined cylindrical ball-bearing races, about the alined geometrical axes of which said member is angularly adjustable; respective bearing members carried by said standards, each having a cylindrical ballrace opposed to and forming a pair with a corresponding trunnion-carried ball-race, one of said bearing members being adjustably mounted on its standard so as to be shiftable in a direction transverse to the axis of the trunnion and the other being fixed; two annular series of bearing balls, one mounted under compression between the races of each pair; two annular ball retainers which engage only the balls of respective series to space and aline the balls, said retainers with the balls engaged thereby having limited freedom of motion axially relatively to the trunnion races; diametric thrust bosses on opposite ends of the fixed, standard-mounted race; and means affording opposed thrust faces engaging said bosses, said faces being carried by a trunnion and normal to the axis thereof.

HAROLD R. LARSEN. DANIEL GURNEY.

REFERENCES CITED The following references'y are of record in the file of this patent: v

UNITED STATES PATENTS 

